A number of glass compositions are known for reinforcing composite materials. Typically, glass composition are tailored for making continuous high-strength glass fiber strands with importance placed upon placed upon strength, ease of manufacturing, control of raw materials costs, chemical compatibility and environmental concerns. S-Glass, R-Glass and E-Glass are well known compositions for reinforcing polymer matrix materials to form composite structures. S-Glass is formed primarily of the oxides of magnesium, aluminum, and silicon with a chemical composition that produces glass fibers having a higher mechanical strength than E-Glass fibers. The S-glass composition produces high strength glass fiber for use in high strength applications such as ballistic armor.
R-Glass is another family of high strength, high modulus glasses that is typically formed into fibers for use in aerospace composite applications. The R-Glass family is primarily composed of silicon oxide, aluminum oxide, magnesium oxide, and calcium oxide with a chemical composition that produces glass fibers with mechanical strength which is generally lower than S-Glass fibers. R-Glass generally contains less silica and greater calcium oxide (CaO) than S-Glass which requires higher melting and processing temperatures during fiber forming.
Glass fibers are often used to reinforce polymer matrices. Some polymers are used to form articles that are transparent. It is desirable to have glass fibers that can reinforce such transparent polymers without significantly degrading the transparency or other appearances of the polymers.